The DigiTech SDRUM has no midi input and the producer does not guarantee that it works in sync with other midi devices.
To synchronize the SDRUM with the DittoX4 you can use the TRS output on the front of the SDRUM and a specifically made cable.
Actually this input jack should be used to connect the DigiTech JamSync with a 3.5 mm TRS plug.
Customarily this input sends (but does not receive!) midi clock and start/stop commands.
By using this special cable, the SDRUM can be used as a master clock for delays, loopers and other midi pedals.
Click here for the video of the SDRUM in sync with the DITTO X4.